The present invention relates to a sodium ion absorption inhibitor, a sodium ion excretion accelerator and use thereof. More particularly, it relates to a sodium ion absorption inhibitor and a sodium ion excretion accelerator, which are capable of inhibiting absorption of excessively ingested sodium ions in digestive tracts and thereby showing excellent action to accelerate excretion of the sodium ions into feces, and their application to medicaments.
According to the National Nutrition Survey Results published by the Ministry of Health and Welfare, Japanese have taken at least 11.5 g of salt a day since 1975, and particularly in 1993, a daily salt intake was 12.8 g. Since there is a correlation between a daily salt intake and a crisis rate of hypertension, the Ministry of Health and Welfare is recommending to decrease the daily salt intake to 10 g or less so as to prevent the crisis of hypertension and moreover, stroke and the like. In the U.S., a daily salt intake has been limited similarly and the recommendation of the U.S. Joint Committee proposes that a daily salt intake of patients suffering from hypertension must be controlled to 6 g or less.
Also, it is said that there is also a correlation between a salt intake and a mortality of gastric cancer. According to the data obtained so far, in a district where a salt intake is large, for example, Toyama city or Hirosaki city, the mortality of gastric cancer is high; on the other hand, in a district where a salt intake is small, for example, Beppu city or Okinawa city, the mortality of gastric cancer is low.
It is reported that dietary fibers such as alginate have sodium ion adsorbing capability to some extent (Journal of Home Economnics of Japan, vol. 39, No. 3, p. 187-195 (1988)), but its adsorbing capability was still insufficient.
The excessive salt intake thus has a bad influence on the human body. Accordingly, a strong demand for development of new technique to extracorporeally excrete the excessively ingested salt is required.
Consequently, an object of the present invention is to provide a sodium ion absorption inhibitor and a sodium ion excretion accelerator, which can excrete excessively ingested common salt outside the body positively and safely, and an agent for preventing and treating a disease caused by excessive common salt ingestion.
Thus, the inventors of the present invention have conducted intensive studies in order to find a component having the above-described actions from a broad range of food materials and found as a result of efforts that metal salts (metal salts other than sodium salt) of lambda-carrageenan have excellent sodium ion absorption inhibiting ability and excretion accelerating ability, and can be applied to food and medicaments. Thus, the present invention has been completed.
Accordingly, the present invention provides a sodium ion absorption inhibitor, a sodium ion excretion accelerator, and an agent for preventing and treating a disease caused by excessive common salt ingestion, which comprises a metal salt (but excluding a sodium salt) of lambda-carrageenan as an active ingredient.
The lambda-carrageenan (xcex-carrageenan) for use in the present invention is a component contained in carrageenan which is broadly used as stabilizing agents, dispersing agents, and the like, such as gelling agents, cosmetics and the like.
Carrageenan is a sticky polysaccharide obtained from red algae, such as the genus Chondrus, the genus Gigartina, and the like (e.g., Chondrus crispus (Irish moss), Gigartina stellata, G. acicularis, G. pistillata and G. radula, which belong to the order Gigartinaceae, species of Fursellaria, Hypnea, Euchema, and the like), of which a component that precipitates in a gel form from a hot water extract with potassium chloride is kappa-carrageenan (xcexa-carrageenan), and the unprecipitated supernatant fraction (a component which is soluble in a potassium chloride solution) is xcex-carrageenan.
xcex-Carrageenan does not contain a. 3,6-anhydro derivative found in the xcexa-fraction, but is a galactan sulfate which is mainly constituted by a constituting monosaccharide D-galactose (D-Gal), particularly a galactan sulfate formed by the alternate bonding with xcex2-(1,4) and xcex1-(1,3) bonds. xcex-Carrageenan is on the market and is easily available.
The above-described metal salt (but excluding sodium salt) of xcex-carrageenan is used in the present invention. Examples of the metal salt include all metal salts, such as alkali metal salts (but excluding sodium salt), alkaline earth metal salts and the like. Potassium salt, calcium salt, magnesium salt and iron salt are particularly preferred.
The above-described red algae is extracted, for example, using hot water of from 60 to 100xc2x0 C., preferably from 80 to 90xc2x0 C., for from 30 minutes to 3 hours, preferably about 1 hour, to obtain a hot water extract of carrageenan. The metal salt of xcex-carrageenan can be obtained by cooling the hot water extract, adding potassium chloride thereto, removing the thus formed precipitate, adding metal halide, such as calcium chloride or the like, to the resulting supernatant, stirring the mixture to completely dissolve the halide, removing low molecular weight substances by dialysis and then allowing the solution to stand for a predetermined period, generally from 2 hours to 24 hours. Alternatively, commercially available xcex-carrageenan may be used instead of the above-described hot water extract of carrageenan.
The thus obtained xcex-carrageenan metal salt may be used as such or optionally after further purification by alcohol precipitation, ion exchange resin chromatography, gel filtration chromatography and the like.
Desirable physical properties of the thus obtained xcex-carrageenan metal salt are as follows.
The xcex-carrageenan metal salt of the present invention has sodium ion absorption inhibiting ability, and, particularly when it is orally administered, it inhibits absorption of sodium ions in digestive tracts and accelerates their excretion.
Consequently, it is effective as a sodium ion absorption inhibitor and a sodium ion excretion accelerator, and can be contained in various foods and the like. Particularly, it can alleviate common salt restriction for patients suffering from various diseases caused by excessive common salt ingestion, such as hypertension, gastric cancer and stroke, so that it is useful as medicaments for preventing and treating such diseases. Also, since it excretes a large amount of sodium ions into feces, it is particularly useful for excreting sodium ions from patients having reduced renal functions, such as renal disease and the like.
The sodium ion absorption inhibitor, sodium ion excretion accelerator and medicament of the present invention which comprise the metal salt of xcex-carrageenan can be produced by processing the xcex-carrageenan metal salt obtained by the above-described method into various forms. Their examples include solids form materials, liquid form materials, emulsion form materials, paste form materials and the like.
The sodium ion absorption inhibitor and sodium ion excretion accelerator of the present invention can be applied to foods effectively. Examples of the foods containing these sodium ion absorption inhibitor and sodium ion excretion accelerator include any one of those which can be ingested immediately as such, are ingested after carrying out cooking and the like, and are premixed materials for use in food production. The solids form materials may be any of powder forms, granular forms and solid forms, and examples include various confectionery, such as biscuits, cookies, cakes, snacks, rice crackers, and the like, bread and powder drinks (powder coffee, cocoa, and the like) Examples of the liquid form, emulsion form and paste form materials include various drinks, such as juices, carbonated drinks, lactic acid drinks, and the like.
Examples of the medicament of the present invention include tablets, powders, granules, fine particles, solutions, and the like, and these preparations can be produced by making the hot water extract of the present invention and a pharmaceutically acceptable carrier into desired forms in the conventional way.
The metal salt of xcex-carrageenan of the present invention has an ability to excrete and absorb about 1 g of common salt (about 400 mg as sodium ions) based on about 10 g of the salt. Thus, using this ability as a standard, it is preferred to take it in an amount of approximately from 10 to 50 g calculated as the metal salt of xcex-carrageenan.